Apparatus for imparting high energy to charged particles



0, 1949. w. F. w sTENboRP 2,480,169

APPARATUS FOR IMPARTING HIGH ENERGY TO CHARGED PARTICLES Filed 001;. 26,1946 5 Sheets-Sheet l lhVentor; Willem F. Westendorp,

His Attorneg.

Aug. 30, 1949. w. F. WESTENDORP 2,480,169

APPARATUS FOR IMPARTING HIGH ENERGY TO CHARGED PARTICLES Filed Oct. 26,1946 3 Sheets-Sheet 2 N Fig.4.

27 Ihve'ntor'.

Aug. 30 1949-. v w. F. WESTENDORP 2,480,169

1 APPARATUS FOR IMPARTING' HIGH ENERGY To CHARGED PARTICLES Filed Oct.26, 1946 y s Sheets-Sheet 3 Fig.8.

l nvehtcrz Willem F. Westendorp,

patenteci Aug. 30, 1949 APPARATUS FOR IMPARTING HIGH ENERGY TO CHARGEDPARTICLES Willem F. Westendorp, Schenectady, N. Y., assignor to GeneralElectric Company, a corporation of New York Application October 26,1946, Serial No. 705,923

13 Claims. 1

The present invention relates to apparatus for imparting high energy tocharged particles by repeated acceleration of such particles.

The invention is applicable in connection with apparatus of the typedisclosed in United States Patent application Serial No. 639,462, filedJanuary 5, 1946 in the names of Herbert C. Pollock and Willem F.Westendorp and assigned to the General Electric Company, a corporationof New York. Such apparatus comprises means for initially acceleratingcharged particles by the action of a field produced by a time varyingmagnetic flux and for thereafter producing continued acceleration ofsuch particles by a localized electric field of cyclically varyingcharacter. My present invention is primarily concerned with theprovision of improved apparatus of this character.

One object of the invention is the provision of a structually compactequipment in which the mass of the magnetic system is appreciablyreduced over designs previously available.

A further object of the invention is to provide a construction whichpermits ready access to the discharge vessel within which chargedparticles are caused to be accelerated and which will lend itselfreadily to bringing out a stream of accelerated particles or a stream ofradiations produced by such particles.

Viewed generally, these objects, together with certain others to bespecified in the following, are realized by the use of a simplifiedmagnetic structure in combination with novel means for energizing thesame.

The features of the invention desired to be protected herein are pointedout in the appended claims. The invention itself, together with furtherobjects and advantages thereof, may best be understood by reference tothe following description taken in connection with the accompanyingdrawings in which Fig. l is a partially sectionalized view of anaccelerator suitably embodying the invention; Fig. 2 is a section online 2-2 of Fig. 1; Fig. 3 is an enlarged view of the discharge vesselof Fig. 1, shown partly broken away; Fig. 4 is a schematicrepresentation of an excitation circuit for the device of Fig. 1 withcertain aspects emphasized by the use of heavy lines; Fig. 5 is adiagrammatic illustration of the magnetic circuit of Fig. 1 in thecondition prevailing during excitation of the heavy line circuit of Fig.4; Fig. 6 is a repetition of a portion of the circuit of Fig. 4 withcertain additional aspects of the circuit being emphasized by heavylines; Fig.7 represents a condition of the magnetic circuitcorresponding to the excitation of the heavy line circuit of Fig. 6;Figs. 8 and 9 are graphical illustrations useful in explaining theinvention; Fig. 10 represents a modification of the invention; and Figs.11 and 12 are graphical representations explaining the operation of Fig.10.

Referring particularly to Fig. 1, there is shown in section a closeddoughnut-shaped glass vessel iii. which defines within its interior anannular chamber Ill. The vessel provides a circular orbit in whichcharged particles (e. g., electrons) derived from a source indicatedgenerally at ll may be accelerated to a high energy level. Afteracceleration, the electrons are to be intercepted by a target H which isoffset from the accelerating orbit. For the purpose of accelerating theelectrons, the vessel is provided internally with means for producing alocalized electric field al ternating at high frequency and thus adaptedto act repeatedly on electrons gyrating within the vessel. The highfrequency electrode system may comprise one of the constructionsdescribed in application Serial No. 691,293 of Anatole M. Gurewitsch,filed August 17, 1946 and assigned to the General Electric Company. Anexemplary construction is illustrated in Fig. 3, which may be regardedas an enlarged partially sectionalized View of the vessel ll] of Fig. 1.The construction illustrated provides on the interior of the vessel It),which is preferably of glass or other suitable dielectric material,highly evacuated, a conductive metal coating l2 consisting, for example,of silver. This coating is longitudinally subdivided by the provision ofuncoated strips 'l3 which have the function of minimizing circulatingcurrents induced in the tube by the changing magnetic field to which thetube is to be subjected as hereinafter described. A gap [4 formedbetween longitudinally spaced portions of the coating provides a regionacross which a high frequency electric field may be established. On theoutside of the discharge vessel It there is provided a second conductivemetal coating [5 which extends over only a portion of the vessel.Coating I5 is electrically connected to the inner coating l2 by twometal rings IT and I8 sealed into the wall of the discharge vessel. Itis to be noted that the ring 18 connects directly with the portion ofthe coating 12 which forms the right-hand boundary of the gap M, whilethe ring I l is connected to the coating 42 at a point which is to theleft of the gap l4 and appreciably spaced from it. Actually, the spacingof the ring I! with reference to the gap I4 is chosen to representelectrically a quarter wave length at the desired frequency of the fieldto be established across the gap I4. With the correct selection oflongitudinal dimensions, the space between the conductors l2 and Iconstitutes in effect a space resonant system comprising a quarter waveconcentric transmission line section. Accordingly, if the structure thusprovided is excited at the proper frequency, a cyclically reversibleelectric field of high intensity may be made to appear across the gapl4. By choosing the frequency of reversal of this field to correspond tothe frequency of rotation of electrons maintained in a circular orbit ofrotation within the vessel l0) an increase in the energy level of suchelectrons may be effected at each traversal of the gap. The frequency ofthis field may be determined as described in a copending application,Serial No. 639,462 by Herbert C. Pollock and W. F. Westendorp, filedJanuary 5, 1946 and assigned to the same assignee as the instantapplication, and may be approximately 57 megacycles for an orbitdiameter of 66 inches. A field of the desired frequency may be suppliedto the quarter wave resonator by means of concentric conductors l9 and20 connected as indicated. The source of high frequency power is notshown but may comprise, for example, an electronic oscillator of knowntype.

The means employed for maintaining in a circular orbit electrons actedupon by the electric field just referred to comprises a magnetic (e. g.,laminated iron) structure represented in Figs. 1 and 2 as including acylindrical core 2| passing through the vessel l0 and consequentlylinking the proposed orbital path of the electron. A duct 2| is providedthrough the core for cooling purposes. The core has at its extremitiesmagnetic members 22 and 23, respectively, which extend radially out andthen converge parallel to the core 2! to provide a gap '25 formedbetween opposed pole pieces 26 and 21. This gap contains the tube I0 andhence the locus of the desired orbital path of the electrons to beaccelerated. Means shortly to be described are provided for productingacross this gap a magnetic guide field which increases in a mannerrelated to the rate of increase in energy of electrons acceleratedwithin the vessel l0. Under proper conditions to be hereinafterspecified, this permits the electric field generated within the vesselacross the gap M to bring the electrons to very high energy levels whilethe electrons are magnetically retained in a stable orbit.

This method of impartin high energy to electrons by the application ofcombined electric and magnetic fields, referred to as the synchrotroprocess, depends among other things upon providing electrons at or nearthe ultimate orbit of gyration at a velocity sufficiently close to thatof light so that they can thereafter be considered to travel at constantspeed, subsequent increments of energy appearing as an increase in mass.Only under these conditions can their traversal of the gap M besynchronized with the cyclical reversals of the constant frequencyelectric field applied to the gap for accelerating purposes.

In the construction of Fig. 3 electrons are pr vided in the evacuatedspace within the discharge vessel in by means of an electron guncomprisin a cathode assembly H and an accelerating and directingelectrode II. These are supplied with potential and, in the case of thecathode, with heating current by means of conductors extendingout-through a stem 30 and connecting with external conductors sealedthrough the wall of the stem. Only the accelerating electrode conductor3| and one of the cathode conductors 32 appear in the drawing. However,electrons so provided are necessarily introduced at relatively lowvelocity, their energy not exceeding one hundred thousand electronvolts, and additional means must be provided for bringing them to a muchhigher velocity before they can be satisfactorily maintained in arelatively fixed orbit by the synchrotron principle. As is explained inthe aforementioned Pollock and Westendorp application Serial No.639,462, this may be done in one way by the use of an initial period ofmagnetic induction acceleration. My present invention is primarilyconcerned with the application of this type of initial acceleration inconnection with a simple, compact and lightweight apparatus.

The magnetic structure of the apparatus of Fig. 1 has already beendescribed as comprising the core 2| and the mutually opposed pole pieces26 and 21. It is particularly to be noted that this structure lacks anexternal yoke or other low reluctance means providing a return path formagnetic fiux tending to leave the upper and lateral surfaces of theparts shown, so that the return of any such flux is necessarily by anair path, inherently of relatively high reluctance. The significance ofthis from an operational standpoint will be indicated later. From astructural standpoint, it presents the advantage of minimizing theweight of the magnetic system and also of increasing the accessibilityof the tube Ill both from the standpoint of manipulating the tube andfrom the standpoint of utilizing high velocity electrons or other highenergy radiations eventually produced by the tube.

For the purpose of energizing the magnetic structure, there are providedseveral sets of coils. One of these, a first magnetizing means, isdesignated as 35 and is arranged so as to embrace only the core 2|. Asecond coil, shown as being divided into two sections 36 and 36, assumedto be connected in series, embraces the complete magnetic structure,including both the pole pieces 26 and 21 and the core 2!. A third coilhaving series connected parts 3'! and 37' also embraces the completemagnetic structure and is adapted when energized to supplement theeffect of the coils 36, 36'. Since these second and third coils bothembrace the complete magnetic structure and therefore produce fluxeswhich have similar effects upon the magnetic circuit, they may beconjointly termed a second magnetizing means. It is proposed in thefollowing to indicate how the various coils just referred to may beenergized in such fashion as initially to permit acceleration bymagnetic induction of electrons introduced within the vessel It] andthereafter to facilitate the continued acceleration of such electrons bythe synchrotron principle, this result being accomplished by a favorablereorientation of the magnetic flux traversing the magnetic structure.

The first phase of operation, that is, the period of magnetic orbetatron acceleration, may best be explained by reference to Fig. 4which shows diagrammatically the energizing circuits used in connectionwith the various coils of the magnetic system above referred to. In thisfigure the portion of the circuit which is active during the period ofmagnetic acceleration has been emphasized by the use of heavy lines inthe circuit diagram. The various magnetizing coils are indicated by thenumbers which identify them in Fig. 1.

The operating cycle may be considered to start approximately at the timeat which electrons are introduced into the discharge vessel l0 (Fig. 3)by application of a pulse of favorable potential to the electrodes IIand H" (shown schematically at the upper right of Fig. 4) The means bywhich this is accomplished are indicated in Fig. 4 as comprising a strip38 of high magnetic permeability material assumed to be so placed as toextend between pole pieces 26 and 21 (Fig. 1) and provided with awinding 39 in which is generated a pulse of voltage as described in U.S. Patent 2,394,071, a vapor discharge valve 42 which is triggered bythis voltage pulse, a capacitor 43 charged from a suitable source ofrectified potential 44 and a pulse stepup transformer 45, The terminalsof the pulse transformer 45 feed the power pulse generated by thedischarge of the capacitor 43 to the electrodes II and II of theelectron gun. As described in the aforesaid U. S. Patent 2,394,071 thetriggering action provided by the winding 39 around strip 38 takes placenear the time in the cycle at which the magnetic field goes through zeroand can be accurately adjusted in time by a direct current bias (notshown) applied to the winding. It is assumed that prior to the time ofelectron injection condenser 40 has been charged from a controlledrectifier source H in the direction indicated by the polarity signsshown in Fig. 4. At or slightly before the instant of electron injectiona controlled gaseous rectifier 4| in series with the condenser 40 istriggered by application of a favorable potential to its grid 4|. Thecircuit by which such triggering is accomplished in proper correlationto the injection of electrons comprises a peak voltage generatingtransformer 41 energized by a phaseshifting network 48 which receivesits power from a source 49 of alternating voltage of the same frequencyas the repetition rate at which the accelerating apparatus is to repeatits cycle of operation.

The firing of the tube 4| places the potential of the condenser 4|]across the coils 36, 36. Moreover, by concurrent triggering by means ofa third winding 41 on peaking transformer 41 of a second controlledgaseous rectifier 50 connected in circuit between the coils 36, 36 andthe coil 35, the latter coil is placed directly in parallel with theformer. Under these circumstances, the coil pair 36, 36' and the coil 35will enclose fluxes inversely proportional to their turn ratio. Byproper selection of this ratio, therefore, the flux traversing thecentral core 2| (Fig. 1) may be maintained in such relation to the fieldexisting between the pole pieces 26 and 21 as to cause electrons withinthe discharge vessel ID to be inductively accelerated while beingmaintained in fixed orbit in accordance with the socalled betatronprinciple. A detailed discussion of the field relationships required inthis connection is given in D. W. Kerst United States Patent No.2,297,305 granted September 29, 1942 and assigned to the GeneralElectric Company. In general, it is required that the followingrelationship be maintained.

Where A is the total change in flux through the electron orbit, r is theradius of the orbit and B .is the flux density of the guide field at theorbit.

In the present connection, fulfillment of this re lationship requiresthe aggregate number of turns in coils 36 and 36 to be appreciably lessthan the turns in coil 35. Because of the parallel connection andinductive coupling of the coils 36, 36' with coil 35, the latter coilwill automatically assumes a current flow opposite to that in the formercoils so that the flux traversing the core 2| may be assumed to be dueto the difference of these currents. This current relationship isschematically indicated by arrows associated with the various coils inFig. 4.

The flux distribution in the magnetic structure during the period nowunder consideration is illustrated in Fig. 5 by the arrows shown appliedto the structure. It will be noted that the flux through the core 2| andthat through the pole pieces 26 and 21 is all in the upward directionwhich implies that its return must be by means of the high reluctanceair path outside the magnetic structure. This is indicated by arrows inproximity to the various surfaces of the magnetic structure. It shouldbe noted, however, that during the period of initial acceleration, themagnetic fluxes involved are relatively weak so that in spite of theinclusion of an air path in the magnetic circuit, they can be obtainedwithout application of excessive power to the energizing circuits.

After the electrons have been brought by magnetic induction to an energylevel corresponding to several (i. e., 2 to 5) million electron volts,their velocity will be within a few percent of the velocity of light andmay thereafter be considered as constant. It is, therefore, possibleafter attainment of such velocity to switchover to the synchrotron typeof operation and thus to carry the electrons to much higher energylevels than would be possible by magnetic means alone.

This means in the first instance that the electrode system providedwithin the vessel ID (Fig. 3) for producing localized electric fields(i. e., across the gap l4) must be energized by the application of ahigh frequency potential through conductors l9 and 2B. This may be doneby the action of a timing circuit including an electronic switchingvalve 5| of the vapor type, and a triggering circuit consisting of apeaked voltage transformer 52 and a phase shifting network 53 connectedto the same source of power 49 as used in conjunction with the firingcircuit of tube 4|. The electronic switching valve initiatesenergization of a high frequency power source 54 which furnishes thehigh frequency potential through conductors I9 and 20 to the electrodesystem associated with gap H (see Fig. 3).

In accordance with my invention, shortly after the high frequencyelectrode system is brought into play switching of the magnetizingcircuit is accomplished to create the closed circuit indicated by theheavy line portion of Fig. 6 in which current is caused to flow seriallythrough coils 31, 31'; 36, 3B and 35.-- This is done by firing tube 60-which may be a controlled gaseous rectifier of the type illustrated or,alternatively, a controlled mercury pool tube. The triggering of thistube is controlled by a timing circuit shown in Fig. e which comprises apeaked voltage producing' transformer 6| connected to a phase shiftingnetwork 62 which is energized by the power source 49.

liminarily charged by a circuit including an appropri'ately timedcontrolled :source 'of some. potential. :Such circuitis assumed to-beincluded in apparatus within the :block outline 7H, and rrra-y comprisea rectifier in which hy means of grid controlled gaseous discharge tubescurrent flow is permitted only "during that jgaart act the cycle ofoperation during which 110 currenitatlows in coilsl'3-l and 3:1.

1 low of current from the: condenser H) reverses the direction of thepotential applied to :the tube 5i] :and thus renders that itube nonlconductive. Conduction of the tube ill may be assumeda-ls'o to :cease,first because 'firingof tube 'fifi timed to occur at a point when thecondenser lil ds essentially discharged, andsecondly, because theapplicationof thetpotcntia-l of the condenser 5H] through discharge tubeBil renders the common terminal of coils 36 and :35 negative.

The effect of the various coils .35, Eli and v3.1

under the conditions indicated in 6 is :such a as considerably toincrease the magnetic .ifield. in qe space between the rpole pieces 28and 2-1 -('i. e, at the-electron :orbit) it is to he noted, moreover,that since the coils 2'36, 36 :are no longer connected in parallel withthe coil 35., 1a 'reversalof flux through the latter ceilrmay Land, inrant, does occur. With :this reversal, *rthe core 2 I now serves as'a'lowreluctancezreturn path-for flux passing between the pole pieces'25 Land 211 so that the need for-suchffiux m returncby the highreluctance air path external Lto the magnetic structure no longerexists. This condition is 'illustrated in Fig. '7 :bythearrows'associated with the magnetic structure illustrated 1 in thatl'figure.

As a matter of fact, by choosing *theznmnberwi turns in coils 31, 31' sothat the totaliturns'zprovided b coils-sfi and 36' plus s l ian'd 231"-=isequal tothe number of turns in coil 35, thetendcncy 'oi flux toleave the top -or lateral smfaces or magnetic structure can beessentially 'suppress'ed. Accordingly, by continuing concurrently toincrease the energization of the various c'oils "(-i.e., .by supplyingthem in s'eries'as'indioated in Fig. 6) the flux traversing-themagnetic-strncture can be increased to a relatively high level withoutexcessive application of magnetizing power because of the fact thatsubstantially all the confined "to a low reluctancepath. -nccordin'gly,a field can be maintained in 'the -gapbetween' the pole pieces 26 and2"! sufiicient to"hold -eledtrons in the desired orbit even though suchelectrons are brought to very high energy levels by the continued actionof the "localized "electric new impressed across the gap f d in'thehighfrequency electrode system (Fig. 3).

'It will be 'noted,-of course,*that the effects just described arerealized by reversalof the "flux passing through the core 21 *with aconsequent reversal of the "forces applied inductively by such field tothe electrons within the discharge vessel. However, such reversed forcesare relativel inconsequential in comparison with the opposit and muchgreater accelerating effect of the localized electric fieldspro'ducedbyth'ehigh frequency electrode system. (ion'sequentl'y, this negativebetatron'action can readily 'be tolerated for the sake of 'theimproveddistr'ibutiono'f the magnetic flux'to which it is: attributable.*The'net' effect of the arrangement described is to provide an aprates:may Jae aptly summarized by reference to the graphical representationsof Figs. 8 and .9. The curve B0 of Fig. 8 represents the :magnetic fieldstrength atthe electron orbit whereas :the curve 111:: of :9 representsthe variations .in flux through the magnetic core 21 (Fig. 1). The coils'35, '36 and -:the coil 35 are energized at the tin-19.121 (i. e.,-by=switching of the tubes 4| and 50, 4) with resultant discharge of thecondenser 40. -At this time or shortly thereafter electrons are'iniected-into the-discharge vessel. The :field Bo and theflux oecontinue to build up along a smoothcurve as indicated until a time 152at which time the tube (Fig. 6) fires. Applicationhf potential :to thehigh frequency electrodes contained within the "vessel 10 may beinitiated at a-time'tir which somewhat precedes the time-taco that Iaslight overlap of the periods of betatron and synchrotron operation'isrealized.

:At the time tz'discharge of current .-from the condenser 10 =(-Fig. :6)which should be charged to apotentialsmaterially above themaximumpotentia-l of the condenser 40, produces an abrupt accelerationofthe rate of growth of the field Bo with an attendant reduction andeventual :retarsal of'the flux 1,250 as previously explained. Thisgrowth! of the guide-field continues until a wtlme ta at which-thecondenser (T0 is wholly discharged. The time its corresponds to theattainment of maximum energy of the accelerated electrons.:AccordmglyJmeans must be provided f or shifting :the (orbit 0f theaccelerated electrons to :cause them tobe intercepted by the'target I li (Fig. \1) which, as :previously explained, is somewhat lolfsetfrom-the accelerating orbit. The orbit ;shiftring 1 means EfOTm no partof my present invention and are, therefore, not particularly describedherein. lIlhey'inay, however, be of the character specifiedinmyipriorPatent No. 2.394,!)72, granted February 5, i946 and :assignedto the General ElectricvCompany, which describes means for: dis-;placing the electron orbit axially -'of the discharge avessel-to causeitto xbe intercepted at the end of the accelerating cycle.

By the time point t; is reached, the --energy originally stored in thecondenser H3 is effectively transferred'tothemagnetic field linking thecoils 3l5'to $1, inclusive. rIn accordance with EKDOWII gprinciplesvof-oscillating circuits, this energy will iirendtorreturn to capacitivestorage :by progressive diminution and eventual reversal of currentZflow in the circuit containing the condenserxand the coils. Accord nglyhe field Bo and the "flllX be will \return to :zero valueat "a time 454.At :this "time atube i 80 is i made conductive in place of the :tube Bil(which concurrently becomes [non-iconductive 'rbBCaIZSB'E'O'f thereversal of the potential applied to it) "thus permitting a reversal :ofthe current flow through the coils v3&3 to :31 and comgpleti'onof theoscillatory cycle. Conductivityxof tube-itlllds controlled :by a timingcircuit including aiphase shifting networkBl and a peaked voltagegenerating transformer 82. At the time indicated "at-i5, B0 and the flux(WWW-11 have 565 again freturnedwtofzero =Ilevel and with the tubes 41,50 and i611 biased to cutoff the'operatingicycie will terminate.Afterthe :completeffull wave cscillation'has taken place, capacitor ll]is TeStOllfiZl -to-'-its-'-original polarity? if "not'uuite to itsoriginal paratus in'which arelatively light and-compact 1 vol'lmagneti'c structure is enabled to perform the functions essential bothto an initial period of hetatron'operation and ensuingperiodpfsynchrotron operation.

The duration of a. given cycle of operation may be from severalthousandths of a second to about ea sixtieth-nf rarse'cond. and thecycle may bearespeated Pat lfrom worse to :sixty times 1 per second.

The complete cycle -of operation of the :nppa- .175 The cycle dengtnisdetermined mainly by :the

circuit constants, whil the repetition rate may be controlled by thechoice of appropriate means for timing the triggering of the tubes 4|and 50.

In a modification of the invention, continuous operation may be obtainedby means of the circuit of Fig. 10 which uses a saturating reactor I inplace of the tubes 60 and 80 of Fig. 6. This has distinct advantageswhere it is convenient to use an operating frequency of sixty cycles persecond and the power can be obtained directly from a supply line. Thismodification is illustrated in Figs. to 12 in which Fig. 10 showsschematically a circuit embodying it, curves V and I of Fig. 11represent voltage and current conditions which might obtain in animagined (but not actually realized) condition of operation of thecircuit, and curves Va. and B0 of Fig. 12 represent, respectively, thevoltage appearing across the coil I03 of Fig. 10 and the field strengthdeveloped at the electron orbit by the actual operation of the circuit.

In Fig. 10 coils IOI, IOI', I02, I02 and I03 are assumed to correspondto the similarly disposed coils of Figs. 4 and 6, and are to beconsidered as being associated with a magnetic structure and dischargevessel in the manner illustrated in Fig. 1. The portion of theenergizing circuit described in Fig. 4 as controlling the synchrotronportion of the operating cycle includes the saturating reactor I00 whichcomprises, for example, a winding with a closed high perme abilitylaminated core. It has a relatively high inductance when the currentdrops below 1% or 2% of the anticipated crest value but has negligibleinductance when saturated by higher current values. The power input forthe synchrotron portion of the illustrated circuit comprises a highvoltage supply line I05 which may be a 60 cycle sine wave source. Thisis connected across a condenser I06 and, ignoring certain otherconsiderations shortly to be specified, tends to produce a current whichis nearly sinusoidal as shown by the curve I of Fig. 11. However, such acurrent, if produced, would have flattened regions as indicated at asnear its zero values because of the high inductance which the reactorI00 attains at these points. The voltage across coil I03 correspondingto current curve I would take the form indicated by the curve V.

At periods when the reactor I00 is saturated, most of the voltageimpressed across the condenser I 06 appears across the coils IOI to I03and serves to produce series current flow through these coils of a formconsistent with the curve I of Fig. 11. This portion of the cycle is,therefore, favorable to synchrotron acceleration of electrons within thedischarge vessel assumed to be associated with the coils.

However, prior to attainment of such synchrotron operation and when thecurrent is approaching zero value as at an in Fig. 11, the reactor I00takes a large share of voltage because of its relatively increasedinductance. The interposition of this high inductance may be said toisolate coil I03 from condenser I06 during the low current intervals.This circumstance makes it possible to cause betatron action to occurduring these intervals.

This is accomplished by triggering the tubes I08 and I09 at a time to(Fig. 12) which corresponds to the attainment of zero value of the 1 beassumed to be of the character of those illustrated in Fig. 4.Triggering these tubes applies the voltage of a condenser III, chargedfrom a properly controlled D.-C. source, including transformer H2 andrectifiers II3, to the polarity indicated in Fig. 10 to the coils IOI,IN and I03 in parallel, thus causing a reversed or negative voltagesuddenly to appear across these coils as indicated at 11, Fig. 12. Thisvoltage immediately starts to decay in the positive direction ascondenser III discharges. The voltages across IN, IN and I03 being nowidentical as a result of their parallel connection, the relationship ofthe gap field and the core flux may be fixed in accordance with theinverse ratio of their turns as previously described, and by properchoice of the turn ratio betatron action may be obtained. The voltage ofcapacitor III does not appear directly through tube I03 across the coilsI02, I02 because of the isolating effect of the reactor I00 which thusprevents an exchange of energy between capacitors I06 and III throughtransformer action of the closely coupled windings IM and I02. Duringthis part of the operating cycle the flux through the core of themagnetic structure and the guide field within the gap are codirectionaland a certain proportion of the magnetic flux is forced to return by anair path exactly as indicated in Fig. 5.

During the betatron part of the cycle, the parallel connection of coilsIOI, IOI' and I03 through tube I 09 offers a low inductance circuit anda fast discharge takes place through tube I08, leaving condenser IIIwithout charge. When condenser III is discharged, coils I 0|, IN and I03lose their applied voltage from this source and tube I03 stopsconducting. By virtue of saturation of reactor I00 which acts as aswitch in this connection, flow of series current through coils IOI toI03 from voltage source I05 and condenser I06 is resumed, and thecircuit reverts to the synchrotron cycle at or soon after time iii. Thehigh frequency electric field is applied at or just before t2, and at orshortly after t2 the fiux in the magnetic core reverses with respect tothe guide field as explained in connection with Fig. '7. Thus electronsbrought to an energy level of several million electron volts by theinitial period of betatron action are subsequently carried to muchhigher levels by synchrotron action.

In all other respects (i. e., with reference to disturbance of the orbitof the accelerated electrons and their useful employment) the operationof the circuit of Fig. 10 is the same as that of the arrangement of Fig.1.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Apparatus for accelerating charged particles in a circular orbitcomprising electrically energized means inductively coupled with saidorbit for producing a time-varying magnetic flux linking the said orbitand a codirectional time-varying magnetic guide field coextensive withsaid orbit, the path of said flux including a low reluctance portion anda high reluctance portion, further electrically energized means coupledwith said orbit and operative after initial acceleration of saidparticles by the action of said flux to additionally accelerate them byanother mechanism, and energy-directing means operative concurrentlywith said last-named means to increase said guide field by reorientingsaid fiux to confine it to the low reluctance portion of said path.

2. Apparatus for accelerating charged particles assures along an orbitalpath, :including magnetic means inductively coupled with said path forproducing an increasing magnetic 'flux linking said path to effectinitial inductive acceleration of said part1 cles and for furtherproducing anincreasing magnew guide field codirectional with said fluxand extending throughout the locus of said path, whereby the acceleratedparticles are maintained in said path, secondary accelerating meanselectrostaticall coupled with said path and acting on said particlesafter sai'd'initial inductive acceleration thereof, and energy-directingmeans operative during the action of said secondary acce1- crating meansto increase the magnetic guide held by relatively decreasing andeventually re versing said flux whereby the accelerated particles arecontinuously maintained in "said path with minimum magnetic energizationof said apparatus.

3. Apparatus for accelerating charged 'parti cles along an orbital path,including a magnetic structure having a core linking said path and a gapcontaining the locus ofs'aid path, coil means magnetically coupled withsaid "structure for en-- ergi'zi'n'g said structure to produce anincreasing magnetic flux through said core to effect initial inductivez'iccel'eration of said particles and fur; ther to produce an increasingmagnetic field said gap codirectional "with said flux whereby theaccelerated particles are maintained in said path, secondaryaccelerating means coupled with said path and acting on said particlesafter said initial inductive acceleration thereof, and energydirectingmeans operative during the action of "said secondary acceleratingmeansto increase the magnetic held in said gap by relativel decreasing andeventually reversing the flux through said core whereby the acceleratedparticles are contlnuouslymaintained in said path with minimumen'ergizaticn oi the magnetic structure.

4. Apparatus for accelerating charged particles along an orbital path,including a magnetic structure having "2, COTE Tinkill'g said path and agap containing the locus of said path, c'oil means mag'netically coupledwith said structure for energizing saidst'ructure to produceall-increasing magnetic flux through said core to effect initialinductive acceleration of said particles and further to produce anincreasing mag'ne'tic field in Said gap codir'ec'tional with said'fi'ux, whereby the accelerated particles are maintained in said path,electrode means electrostatically coupled tiffth said path 'forproducing a localized electric field acting on said particles to furtheraccelerate them after their initial inductive acceleration, andenergy-directing means operative during the action of said electriclie-1d .to increase the magnetic field in said gap by relativelydecreasing and eventually reversing the flux through said core, wherebythe accelerated particles are con tinuously maintained in said path withminimum energiz'ation of the magnetic structure.

5. Apparatus for accelerating charged particles along an orbital pathcomprising a magnetic core linking said .p'ath, magnetic membersextending radially out from the extremities of said core and thenconverging parallel to said core to ,provide between them an annular gapcontaining the locus of said path, first magnetizing means embracingonly said core, second magnetizing means embracing both the core andsaid outlying member's, means for initially energizing both saidmagnetizing means to produce an increasing magnetic liu'x through saidcore and a codirec- 't'i'on'al increasing magnetic guide field in saidgap,

thereby inductively accelerating said particles, secondary acceleratingmeans electrostaticaliy coupled with said path and acting on saidparticles after initial inductive acceleration thereof, and meansoperative during the action of said secondary means to modify theenergization of said first and second magnetizing means so that saidguide hold is increased by decreasing and eventually reversing said fluxwhereby the accelerated particles are continuously maintained in saidpath with minimum magnetization of said apparatus.

6. Apparatus for accelerating charged particles along an orbital pathcomprising a magnetic core linking said path, magnetic members extendingradially out from the extremities of said core to provide between theman annular gap containing the locus of said path, a first coil enclosingonly said cor-e, second coils enclosing both the core and said outlyingmembers, means for initially energizing both said coils in parallel toproduce an increasing magnetic flux through said core and acodirectional increasing magnetic guide field in said gap, suc-henergization of said coils causing said particles to be maintained insaid path by said guide field while being accelerated by said flux,secondary electrically energized accelerating means coupled with saidpath and acting on said particles after initial illductive accelerationthereof, and-energy-directing means operative during the action of saidsecondary means to modify the energization of said coils by connectingthem in series so that said guide field is increased by decreasing andeventually reversing said whereby the accelerated particles arecontinuously maintained in said path with minimum magnetic energizationofsaid apparatus.

7'. Apparatus for accelerating charged particles along an orbital pathcomprising a magnetic core linking said path, magnetic members extendingradially out from the extremities of said core and then convergingparallel to the core to provide between them an annular gap containingthe locus of said path, 'a first coil enclosing only said core, secondcoils enclosing both the core and said outlying members, means forinitially energizing both said 'coils in parallel to produce anincreasing magnetic flux through said core and a cod-irectionalincreasing magnetic guide field in said gap, such energization of saidcoils causing said particles to be maintained in said path by said guidefield while being accelerated by said flux, secondary accelerating meansacting on said particles after initial inductive acceleration thereof,and switching means operative substantially concurrently with theenergize,- tion of said secondary accelerating means to change theparallel 'energi'zati'on of said coils to series energiz'ation, wherebysaid guide field is increased by decreasing and eventually reversingsaid flux.

-8. Apparatus for accelerating charged particles along an orbital pathcomprising a magnetic core linking said path, magnetic members extendingradially from the extremities of said core to provide between them anannular gap containin-g'the locus of said path, a first c'oil embracingonly said core, a second coil embracing both the core and said outlyingmembers, means for initially energizing both said coils in parallel toproduce an increasing magnetic flux through said core to accelerate saidparticles and a codirectional increasing magnetic guide field in saidgap to maintain the accelerated particles in said path,

the return of flux traversing said core and said members being by an airpath outside said members, secondary accelerating means acting on saidparticles after initial inductive acceleration thereof, and meansoperative during the action of said secondary means to change theenergization of said coils from parallel to series and concurrently tosupplement the magnetizing eifect of said second coil so as to producean increase in said guide field by reducing and eventually reversingsaid flux, whereby the accelerated particles are continuously maintainedin said orbital path without any substantial increase in the fluxtraversing said air path.

9. Apparatus for accelerating charged particles along an orbital pathcomprising a magnetic core linking said path, magnetic members extendingradially out from the extremities of said core and then convergingparallel to the core to provide between them an annular gap containingthe locus of said path, a first coil enclosing only said core, a secondcoil enclosing both the core and said outlying members, means forinitially energizing both said coils in parallel to produce anincreasing magnetic flux through said core and a co-directional magneticguide field in said gap whereby said particles are concurrentlyinductively accelerated and maintained in said path, secondaryaccelerating means acting on said particles after initial inductiveacceleration thereof, a third coil enclosing both said core and saidoutlying members, a voltage source adapted to energize said coils inseries, and a switching circuit including a reactor which saturatessubstantially concurrently with the energization of said secondaryaccelerating means to connect said coils in series with said voltagesource, whereby said guide field is substantially increased bydecreasing and eventually reversing said accelerating flux.

10. Apparatus for the acceleration of charged particles along an orbitalpath comprising: a magnetic core linking said path; magnetic membersextending radially outward from the ex tremities or" said core toprovide between them an annular gap; an annular evacuated envelopecontaining the locus of the path within said annular gap; a source ofcharged particles adjacent the locus of said path within said envelope;an alternating voltage source; an energy supply circuit for controllingthe release of charged particles into said path from said particlesource in dependence upon the cyclical variations of said voltagesource; first coil means enclosing only said core; second coil meansenclosing both said core and said outlying members, said first andsecond coil means being electrically connected in parallel through afirst switching device; a second switching device and an electricalenergy storage device forming a series circuit which is connected acrossthe parallel circuit comprising said first and second coil means; atriggering circuit controlled by said voltage source and connected toapply a triggering voltage to said first and second switching devices atapproximately the time of release of particles into said path so thatsaid energy storage device may discharge through the parallel circuitcomprising said first and second coil means, the efiect of such parallelexcitation of said coil means being to produce fluxes in said centralcore and said gap which are co-directional whereby said particles areinductively accelerated along said path by said core flux while beingmaintained in the path by the field corresponding to said gap flux; highfrequency electrode means energized in timed relation to the variationsof said voltage source and electrostatically coupled to said path byproximity thereto to supply additional energy to said particles aftersaid inductive acceleration thereof; a circuit connected in parallelwith said first switching device including the series combination ofthird coil means embracing both said core and said outlying members, afurther energy storage device and a third switching device, said thirdcoil means being connected to induce'a magnetic field co-directionalwith that of said first coil means when energized in series therewith;and triggering means controlled from said voltage source to supply atriggering voltage to said third switching device after initiation ofthe operation of said high frequency electrode means whereby saidfurther energy storage device may discharge serially through said first,second and third coil means to increase said guide field by intensifyingthe flux in said gap and consequently reversing the fiux in said core sothat the particles are continuously maintained in said path in spite ofthe additional acceleration imparted to them by said high frequencyelectrode means.

11. Apparatus for the acceleration of charged particles along an orbitalpath comprising: a magnetic core linking said path; magnetic membersextending radially outward from the extremities of said core to providebetween them an annular gap; an annular evacuated envelope containingthe locus of the path within said annular gap; a source of chargedparticles adjacent the locus of said path within said envelope; analternating voltage source; an energy supply circuit for controlling therelease of charged particles into said path from said particle source independence upon cyclical variations of said voltage source; first coilmeans enclosing only said core; second coil means embracing both saidcore and said outlying members, said first and second coil means beingelectrically connected in parallel through a first controlled rectifier;a second controlled rectifier and a capacitor forming a series circuitwhich is con: nected across the parallel circuit comprising said firstand second coil means, said capacitor hav ing a charging circuitconnected thereto and controlled by said source of alternating voltagewhereby said capacitor may be charged to a desired potential in timedrelation to the cyclical variations of said voltage source; a triggeringcircuit controlled by said voltage source and connected to apply atriggering voltage to said first and second controlled rectifiers atapproximately the time of release of particles into said path so thatsaid capacitor may discharge through the circuit comprising said firstand second coil means, the effect of such parallel excitation of saidcoil means being to produce fluxes in said central core and said gapwhich are co-directional whereby said particles are inductivelyaccelerated along said path by said core flux while being maintained inthe path by the field corresponding to said gap flux; high frequencyelectrode means energized in timed relation to the variations of saidvoltage source and electrostatically coupled to said path by proximitythereto to supply additional energy to said particles after saidinductive acceleration thereof; a circuit connected in parallel withsaid first controlled rectifier including the series combination ofthird coil means embracing both said core and said outlying members, afurther capacitor and a third controlled rectifier, said third coilmeans being connected to induce a magnetic field co-directional withthat of said first coil means when energized in series therewith; andtriggering means controlled from said voltage source to supply atriggering voltage to said third controlled rectifier after initiationof the operation of said high frequency electrode means whereby saidfurther capacitor may discharge serially through said first, second andthird coil means to increase said guide field by intensifying the fluxin said gap and consequently reversing the flux in said core so that theparticles are continuously maintained in said path in spite of theadditional acceleration imparted to them by said high frequencyelectrode means.

12. Apparatus for the acceleration of charged particles along an orbitalpath comprising: a magnetic core linking said path; magnetic membersextending radially outward from the extremities of said core to providebetween them an annular gap; an annular evacuated envelope containingthe locus of the path within said annular gap; a source of chargedparticles adjacent the locus of said path within said envelope; analternating voltage source; an energy supply circuit for controlling therelease of charged particles into said path from said particle source independence upon the cyclical variations of said Voltage source; firstcoil means enclosing only said core; second coil means enclosing bothsaid core and said outlying members, said first and second coil meansbeing electrically connected in parallel through a first switchingdevice; a second switching device and an electrical energy storagedevice forming a series circuit which is connected across the parallelcircuit comprising said first and second coil means; a triggeringcircuit controlled by said voltage source and connected to apply atriggering voltage to said first and second switching devices atapproximately the time of release of particles into said path so thatsaid energy storage device may discharge through the parallel circuitcomprising said first and second coil means, the effect of such parallelexcitation of said coil means being to produce fluxes in said centralcore and said gap which are co-directional whereby said particles areinductively accelerated along said path by said core flux while beingmaintained in the path by the field corresponding to said gap flux; highfrequency electrode means energized in timed relation to the variationsof said voltage source and electrostatically coupled to said path byproximity thereto to supply additional energy to said parand secondswitching devices to be extinguished and said first, second and thirdcoil means to be connected in series circuit whereby said further energystorage device may discharge through said last-named series circuit toincrease said guide field by intensifying the flux in said gap andconsequently reversing the flux in said core so that the particles arecontinuously maintained in said path in spite of the additional iii.

16 acceleration imparted to th m y d h h quency lectrode means.

13. Apparatus for the acceleration of charged particles along an orbitalpath comprising: a magnetic core linking said path; magnetic membersextending radially out from the extremities of said core to providebetween them an annular gap; an annular evacuated envelope containingthe locus of the path within said annular gap; a source of chargedparticles adjacent the locus of said path within said envelope; meansincluding an alternating voltage source for controlling the release ofcharged particles into said path in dependence upon the cyclicalvariations of said voltage source; first coil means enclosing only saidcore; second coil means embracing both said core and said outlyingmembers, said first and second coil means being electrically connectedin parallel through a first controlled rectifier; a second controlledrectifier and a capacitor forming a series circuit which is connected inparallel with the parallel circuit comprising said first and second coilmeans; a charging circuit connected between said source of alternatingvoltage and said capacitor whereby said capacitor may be charged to adesired potential in timed relation to the cyclical variations of saidvoltage source; a triggering circuit controlled by said voltage sourceand connected to apply a trigger ing voltage to said first and secondcontrolled rectifiers at approximately the time of release of saidparticles into said path whereby said capacitor may discharge throughthe parallel circuit comprising said first and second coil means toproduce an increasing magnetic flux through said core and a(co-directional magnetic guide field in said gap, said field and, saidflux causing said particles to be inductively accelerated along saidpath; high frequency electrode means energized in timed relation to thevariations of said voltage source and electrostatically coupled to saidpath to supply additional energy to said particles after said inductiveacceleration; a circuit connected in parallel with said first controlledrectifier including third coil means em.- bracing both said core andsaid outlying members, a capacitor connected to be charged in timedrelation to the variations of said source and a third controlledrectifier, said third coil means being connected to induce a magneticfield codirectional with that of said first coil means when energized inseries therewith; and a triggering circuit energized from said sourceand connected to supply a triggering voltage to said third rectifierafter imitation of the operation of said high frequency electrode meanswhereby said lastnamed capacitor may discharge serially through saidfirst, second, and third coil means to increase said guide field so thatthe particles are continuously maintained in said path in spite of theadditional acceleration imparted by said high frequency electrode means.

WILLEM F. WESTENDORP.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,103,303 Steenbeck Dec. 28, 19372,229,573 Jonas Jan. 21, 1941

